Field
Certain embodiments of the present invention may relate to latency reduction, associated with semi-persistent uplink scheduling.
Description of the Related Art
Long-term Evolution (LTE) is a standard for wireless communication that seeks to provide improved speed and capacity for wireless communications by using new modulation/signal processing techniques. The standard was proposed by the 3rd Generation Partnership Project (3GPP), and is based upon previous network technologies. Since its inception, LTE has seen extensive deployment in a wide variety of contexts involving the communication of data.
Different methods are used for user equipment (UE) uplink (UL) scheduling. In case of dynamic UL scheduling, when the UE needs to send data in the uplink, it will send a scheduling request (SR) to an evolved Node B (eNB). The eNB will allocate resources to the UE and inform the UE through a Physical Downlink Control Channel (PDCCH channel). In certain situations, it can be more beneficial to use semi-persistent scheduling (SPS). For example, if the amount of UL resources needed is not too high and/or the resources are needed in a known periodic pattern, scheduling can be done at once by the eNB, and the UE can use these resources instead of requesting resources for each transmission time interval (TTI), and therefore reducing control plan overhead. An example case where SPS is useful is the voice-over-IP (VoIP) use case, where adaptive multi-rate (AMR) codec provides packets once per 20 ms during active period. In this case, SPS with 20 ms periodicity can be used.
Up to now, a minimum SPS periodicity, as defined in the specifications, has been 10 ms. However, recently, in the context of latency reduction, an SPS periodicity of 1 TTI has been introduced, which is useful for configuring UE with an UL SPS for latency reduction purposes, as there is no need to send SR before transmitting the data (or transmitting a buffer status report (BSR)) directly using the persistently configured UL grant.